FIG. 9 shows an example of a color image forming apparatus of the prior art. The color image forming apparatus 100 is an apparatus of the tandem type in which four image forming units 101Y, 101M, 101C, and 101K for yellow, magenta, cyan, and black are serially arranged. The yellow image forming unit 101Y comprises: (1) a photosensitive drum 102Y; (2) a charger 103Y, which uniformly charges the surface of the photosensitive drum 102Y; (3) a developer 104Y, which develops an electrostatic latent image formed on the photosensitive drum 102Y for forming a toner image; (4) a transfer charger 105Y, which transfers the toner image to a recording member; and (5) a cleaning box 106Y, which recovers and houses residual toner remaining on the image carrier after transfer. Elements (2)-(5) are arranged around the photosensitive drum 102Y, as illustrated. The magenta, cyan, and black image forming units 101M, 101C, and 101K are configured in the same manner. Thus, the magenta, cyan, and black image forming units 101M, 101C, and 101K, include a photosensitive drum 102M, 102C, 102K,, a charger 103M, 103C, 103K, a developer 104M, 104C, 104K, a transfer charge 105M, 105C, 105K, and a cleaning box 106M, 106C and 106K respectively.
An electrostatic latent image of the yellow component is formed on the photosensitive drum 102Y by the yellow image forming unit 101Y. The electrostatic latent image is developed by the developer 104Y to be formed as a toner image, and the toner image is then transferred to a recording member by the transfer charger 105Y. Thereafter, an electrostatic latent image of the magenta component is formed on the photosensitive drum 102M by the image forming unit 101M. The electrostatic latent image is developed by the developer 104M to be formed as a toner image, and the toner image is then superimpose-transferred to the recording member by the transfer charger 105M. The same procedure is then repeated in the image forming units 101C and 101K. Thereafter, toner is fixed to the recording member by a fixing roller 107, thereby copying or recording a desired color image.
The color image forming apparatus 100 of the prior art has a problem in that it is difficult to reduce the size of the apparatus. This problem is produced because the color image forming units 101Y, 101M, 101C, and 101K have the cleaning boxes 106Y, 106M, 106C, and 106K, respectively, and hence the image forming units 101Y, 101M, 101C, and 101K occupy a large volume.
Japanese Patent Publication (Kokai) Ho. HEI5-53414 discloses a color image forming apparatus in which a part of image forming units has a simplified cleaning box so as to have a cleanerless configuration, thereby intending to reduce the size of the apparatus.
In the color image forming apparatus 200 disclosed in Kokai, the size of the apparatus is reduced, but the degree of the size reduction is not sufficient because a part of the image forming units still include a cleaning box. A cleanerless image forming unit requires a non-contact charger (such as a corona discharger), thereby producing a further problem in that ozone is generated, which causes environmental contamination.